Method and apparatus for recording sound



July 19, 1938.

0. A. Ross 2,124,473

METHOD AND APPARATUS FOR RECORDING SOUND Filed April 21, 1956 oil k9 i2 11 i lullllllllllllllll 9 wt] [3 |||llllll [mm-.

. INVENTOR -|Il l Patented July 19, 1938 UNITED STATES PATENT 2,124,473

METHOD AND APPARATUS FOR RECDED- ING SOUND Oscar A. Ross,

Application April 21,

16 Claims.

This invention relates to photographically recording sound on film and more particularly to that form of recording known as variable density sound recording.

When photographically recording sound through a conventional light valve, the light admitted to the film, neglecting the individual modulations corresponding to the sound waves being recorded, is of substantially constant value and therefore the ground noise, due to graininess of the film, which is, at this time, the only form of ground noise considered, is substantially constant in value. Therefore when sound of comparatively low volume is recorded this ground noise becomes a relatively large and objectionable factor during sound reproduction.

Furthermore, ground noise is also produced by collection of dirt on the sound track and is also further produced by scratches or other blemishes thereon thereby adding to the ground noise produced by graininess of the film. Much ground noise is also produced from improper film processing.

This invention overcomes the foregoing objection by dual control of the sound recording light, one control comprising a light valve responding to the sound vibrations and the other control comprising a light valve responding to the amplitude of the recorded sound. The first named control 30 includes the use of ribbons or other form of light shutters moving in one plane for recording the sound vibration and the second named control includes the use of ribbons or other form of shutter moving in a plane angularly to the plane of movement of the first named ribbons or shutters; the last named ribbons or shutters being moved in response to the amplitude of the sound being recorded.

By the use of the second or amplitude light valve, the width of the sound track on the film is varied, the section of track onto which the low volume sound is recorded being comparatively narrow with respect to the sections onto which high volume or maximum amplitude sound is being recorded. In other words the width of the sound track is varied in proportion to the variation in the amplitude of the sound recorded, being of minimum width at minimum amplitude of recorded sound and of maximum width at maximum amplitude of said sound. A sound track so formed has manifold advantages when employed for reproducing sound. The ground noise produced by the comparatively narrow track sections is comparatively small and therefore does not interfere with faithful reproduction of the recorded sound.

New York, N. Y.

1936, Serial No. 75,515 (01. 1791il0.3)

Any dirt collected on the sound track at said narrow section is insufllcient to produce objectionable ground noise due to the small area onto which said dirt may collect.

Other advantages will be apparent as the description of the invention progresses and the novel and peculiar structure thereof is pointed out in the specification and wherein:--

Figure 1 is a diagrammatic view of one form of the invention, and Fig. 2 is a diagrammatic View of a modified form of the invention, and Fig. 3 is an enlarged plan View of a sound film showing the peculiar sound tracks formed by the invention, and Fig. 4 is a part perspective View of one of the light valves for producing said sound track, and Fig. 5 is a circuit plan of one form of control for the amplitude light valve.

Referring to Fig. 1, light source 3 projecting light through optical system 2 and aperture 3 reaches film 5. Light valve 5 comprises in part magnet l and light modulating ribbon unit 8 the ribbons or shutters of which are arranged to modulate the light of optical system 2 in response to the frequency of the signal or sound waves as more full hereinafter describes. The ribbons of said unit 5 are positioned in a plane at right angles to the plane of movement of film 5 whereby a variable density form of sound record 9 (see Fig. 3) is recorded onto sound track 55.

Light valve I l comprises in part magnet l 2 and light modulating ribbon unit it, the ribbons of which are arranged to modulate the light of optical system 2 in response to variations in amplitude of the sound being recorded as more fully hereinafter described, the light controlling portion of said ribbons being arranged in a plane substantially parallel to the plane of movement of said film whereby the width of the sound track is varied in proportion to the amplitude of the recorded sound.

The ribbons of units 8 and i3 or 33 and 35 form a rectangular opening, one pair of opposite sides of which are shuttered in accord with the frequency of the sound recorded by units 8 or 33, and the opposite pair of sides of which are simultaneously shuttered in accord with the amplitude thereof as recorded by units 53 or Sound waves picked up by a conventional microphone l 5 will modulate the energy in primary circuit #6 including battery ii. The primarily modulated current produces corresponding modulated current in transformer 58, the output of which is amplified by a conventional amplifier E9, the output of said amplifier being jointly connected to light valve unit 8 for vibrating the ribbons thereof in response to the frequency or wave form of the sound, and to the primary of transformer 2!], the output of which is arranged to energize wave dampening unit 2 I, the output of said unit being connected to light valve l3 for vibrating the ribbons thereof in response to variations in amplitude of the sound being recorded.

Fig. 2 shows a modified form of light valve 30 wherein optical system 3! is arranged to project light from source through aperture 3 onto film 5. Light valve 35 comprises in part magnet 32, frequency recording ribbon unit 33 and amplitude recording unit 34.

Referring to Fig. 3, film 5 is assumed to be a negative sound film onto which sound record 9 has been recorded onto sound track it by the sound recording systems as shown in Figs. 1 or 2, the sound record 9 being of the variable density form.

Referring to Fig. 4, showing light modulating ribbon unit [3 in more detailed form, base member 22 originally secured to magnet l2 includes light slit 23 extending transversely with respect to the film travel being arranged on the axis of optical system 2. Ribbons 24 and 25 are tensioned over studs or dampening members 26 by suitable springs not shown. Masking members 21 are secured to each ribbon and extend over slit 23 for masking off all light rearwardly of said ribbon. Stop or spacer members 28 are removably supported by dowel members 29 whereas the ribbons 24 and 25 are shown as positioned adjacent to light slit 23, when base 22 is employed in connection with a single magnet, as shown in Fig. 2, the frequency recording ribbons are placed adjacent said light slit and the amplitude recording ribbons 24 and 25 are arranged thereabove. If desired the frequency recording ribbons may be arranged on one side of base 22 and the amplitude recording ribbons may be ar-' ranged on the opposite side thereof.

Referring to Fig. 5, showing one form of frequency dampening unit 453 which may be employed to eliminate the signal sufficiently to have the light valve unit l3 respond to the amplitude of the sound solely, energy from'transformer 20 is fed to the grid of tube 4! for amplification thereby and thence through choke 32 to tube 53 for further amplification, said choke and condensers A l and 45. acting to assist in reducing the signal modulations to a continuous wave form which varies in amplitude corresponding to the volume of the sound being recorded.

Operation Referring to Figs. 1 and 3, as film 5 advances and sound is directed into microphone l5, light valve 8 photographically records a variable density sound record 9 onto track ID. Simultaneously the light valve l3 varies the width of said sound track as shown by Fig. 3, the Wide portions 55 corresponding to a maximum volume of sound when said sound track is reproduced, and the narrow portions 5! and 52 corresponding to a reduced or minimum volume of sound when said sound track is advanced for reproducing said sound.

Whereas the non-record portion 53 on each side of the comparatively narrow, or low volume track portions are transparent as shown, when negative film 5 is printed onto a positive film said transparent portions will become opaque to light and therefore no ground noise can be produced by these portions due to graininess of the film and therefore ground noise will be reduced to a minimum. It is to be understood that whereas ground noise will be produced in greater proportion at the maximum amplitude sound portions 50 that the comparatively larger volume of sound produced at these points completely overshadows said ground noise thereby producing highly satisfactory sound reproduction.

The operation of light valve 35 shown in Fig. 2 is similar to that described in connection with Fig. 1. The frequency recording ribbon unit 33 photographically recording the sound in variable density form and the amplitude ribbon unit (it simultaneously varying the width of the sound record in response to the amplitude of the sound being recorded, said varying of the track width actingto vary the length of the striations corresponding to the frequency of the sound recorded.

Referring to Fig. 4, whereas the frequency recording ribbons of units 8 or 33 are arranged parallel to the light slit as 23, and therefore can continuously mask the edges of said slit, such is as 13 and 34 are placed transversely of said slit unless said ribbons are made comparatively thick. To permit the use of comparatively thin and therefore more readily responsive ribbons, masks as 21 are secured to the rearward side of said ribbons, extending rearwardly beyond the ends of light slit 23 a sufficient distance whereby said slit is always masked rearwardly of said ribbons. Masks 2'! also act to further dampen out all frequency vibrations of said ribbons which may not be filtered by dampening unit M. Insulation members 28 are provided to positively space ribbons 24 and 25 and prevent their clashing particularly when the frequency of the amplitude variations of the sound may synchronize with the resonant frequency of said ribbon under tension.

It is to be understood that when the volume of the sound recorded increases the ribbons 24 and 25 move away from each other and expose substantially the entire slit when maximum amplitude sounds are recorded and approach each other as the volume of said recorded sound decreases, being in the position shown at minimum or nil sound volume.

Whereas the sound amplitude recording ribbons 24 and 25 are shown as normally tensioned at their minimum amplitude position, they may be normally tensioned at the maximum amplitude position and biased to the minimum amplitude position upon being energized by dampening unit 2|, or they may be normally positioned midway between said minimum and maximum amplitude position and biased to said minimum amplitude position upon being energized by unit 2|.

It is to be understood that suitable masks including a light slit is introduced in the optical systems 2 and 3| for projecting an attenuated light image transversely of the track the width of which is preferably not over one half mil.

This application forms a continuation in part of my application Serial No. 381,793, filed July 29, 1929.

It is to be understood that film 5 is advanced continuously while recording sound and that the mask t prevents stray light from reaching said film, the attenuated light image for recording the sound being formed independently of aperture 3.

What I claim is:

1. In sound recording apparatus for photographically recording sound onto light sensitive film, means for advancing said film continuously in one direction, a source of electrical energy corresponding to sound, means including an optical system for projecting substantially constant intensity light onto said film, a light valve including parallel ribbons in the path of the projected light, means responsive to the modulated energy source for vibrating said ribbons in response to the wave form of said sound for photographically recording a frequency record of said sound onto said film, another light valve including other parallel ribbons additional to said first named ribbons in the path of said light, means responsive to said energy source for vibrating said last named ribbons in response to the amplitudes of said sound for photographically recording an amplitude record of said sound onto the same area of said film onto which said frequency record is recorded simultaneously with the recording of the frequency record thereon.

2. In a light valve for recording sound onto photographic film, a base, a light slit therein, parallel sound recording ribbons tensionly supported by said base extending transversely with respect to said light slit spacedly between the ends thereof, and masks supported by said ribbons rearwardly thereof, the masks extending beyond the ends of said slit for preventing light from passing therethrough.

3. In a light valve for recording sound onto li ht sensitive film, a base, a light slit therein, parallel sound recording ribbons tensionly supported by said base extending transversely with respect to said light slit between the ends thereof, and a fixed spacer between said ribbons positioned adjacent said slit for limiting the movement of said ribbons toward each other to a predetermined amount.

4. In a light valve for recording sound onto light sensitive film, a base, a light slit therein, parallel sound recording ribbons tensionly supported over said light slit extending transversely thereof for recording sound amplitude records on said film and other parallel ribbons tensionly supported over said slit extending parallel thereto for recording a wave form record onto said film.

5. In a light valve for recording sound onto light sensitive film, a base, a light slit therein, parallel sound recording ribbons extending transversely with respect to said light slit spacedly between the ends thereof for recording amplitude records of sound onto said film, and other parallel sound recording ribbons extending parallel to said light slit for recording wave form records of sound onto said film in composite form with said amplitude records.

6. In a light valve for recording sound onto light sensitive film, a base, a light slit therein, means for projecting light of substantially constant value through said slit, parallel recording ribbons vibrated in response to variation in amplitudes of sound extending transversely of said light slit spacedly between the ends thereof for modulating said light through said slit for photographically recording sound amplitude records onto said film, and other parallel recording ribbons vibrated in response to wave forms of said sound extending longitudinally of said slit for photographically recording sound wave records onto said film simultaneously with the recording of the amplitude records thereon.

7. In sound recording apparatus, a light sensitive film, means for advancing said film uniformly, means including a light source for optically projecting substantially constant light onto said advancing film, a source of modulated energy corresponding to sound, a light valve responsive to said modulated energy including parallel ribbons in said projected light extending transversely of said film with respect to the plane of advancement thereof for photographically recording a frequency record of said sound onto said film, and a second light valve responsive to said modulated energy including parallel ribbons in said projected light extending parallel to said film with respect to the plane of advancement thereof for photographically recording an amplitude record of said sound onto the same area onto which said frequency record is recorded simultaneously with recording said frequency record thereonto.

8. The method of photographically recording sound onto light sensitive film which involves, advancing said film uniformly, optically projecting a beam of substantially constant light onto said film, shuttering said projected light in a plane transversely of the plane of advancement of said film in response to energy modulated in accord with the frequency of sound simultaneously with also shuttering said projected light in a plane parallel to the plane of advancement of said film in response to variations in the amplitude of said sound for photographically recording a composite frequency and amplitude record of said sound onto the same area of said film.

9. The method of photographically recording sound onto light sensitive film which involves, advancing said film uniformly, optically project-- ing a substantially constant light past a light opening onto said film, varying the size of the opening in a plane transversely of said opening in response to energy modulated in accord with the frequency of sound simultaneously with varying the size of said opening in a plane parallel longitudinally of said opening in response to energy modulated in accord with variations in the amplitude of said sound.

10. The method of recording sound having frequency and amplitude characteristics which involves, advancing said film uniformly, optically projecting a substantially constant light onto said advancing film, shuttering said projected light in a plane transversely of the plane of advancement of said film in response to energy modulated in accord with one of said sound characteristics simultaneously with also shuttering said projected light in a plane parallel to the plane of advancement of said film in response to energy modulated in accord with variations in the other characteristic of said sound for photographically recording a composite frequency and amplitude record thereof onto said advancing film.

11. In sound recording apparatus, a light sensitive film, means for advancing said film uniformly, means including a light source for optically projecting substantially constant light onto said film as it advances, means responsive to energy modulated in accord with frequency of sound for shuttering said projected light in a plane transversely of the plane of advancement of said film for photographically recording a sound wave record thereonto, and means responsive to energy modulated in accord with the amplitude of said sound for shuttering said projected light in a plane parallel to the plane of advancement of said film for photographically recording an amplitude record of said sound onto the same area of said film onto which said frequency record is recorded jointly. with-thev recording of said frequency record;

12. In apparatus for recording sound having both frequency and amplitude characteristics, a

Ii light sensitive film, means for advancing said film uniformly, means including a light source for optically projecting a substantially constant light onto said advancing film, means responsive to energy modulated in accord with variations of one of said sound characteristics for shutter ing said projected light in a plane transversely of the plane of advancement of said film, and means responsive to energy modulated in accord with variations of said other sound characteristic for shuttering said projected light in a plane parallel to the plane of advancement of said ing onto said film, means operated in response to energy modulated in accord with frequency of sound. for shuttering one pair of opposite sides of said opening for photographically recording sound wave record onto said advancing film,

and means operated in' response to energy modulated in accord with variations in the amplitude of said sound for shuttering theopposite pair of sides of said opening for photographically recording an amplitude record of said sound onto the same area of said film onto which said frequency record is recorded jointly with the recording of said frequency record thereonto.

14. In combination, a source of light, a light sensitive film moved at a constant speed through light from said source and said film, means including shutters vibrated in the direction of motion of said film and shutters vibrated parallel to said film motion, means including an energized circuit responsive to sound to vibrate said first named shutters in accord with frequency of said sound for photographically recording a sound wave record onto said film, and means including another energized circuit responsive to saidsound to vibratesaid second named shutters inaccord withf-the amplitude variations of said sound for photographically recording an amplitude record thereof onto the same area of said film ontowhich saidfrequency record is recorded jointly with the recording of said frequency record-.-

15. In sound recording apparatus, a light sensitive film, means for advancing said film uniformly, means including a light source for optically projecting a substantially constant beam of light onto said film, means including a source of energy modulated in response to sound waves, a pair of ribbons having spaced parallel portions in'said light beam vibrated in response to the frequency of said modulated energy for recording a frequency record of said sound waves onto said film, another pair of ribbons also having spaced parallel portions in said light beam vibrated in response to the amplitude of said modulated energy for recording an amplitude record of said sound waves onto said fihn jointly with said frequency record, a base, means for tensionly supporting said first named pair of ribbons on said base with the spaced parallel portions thereof in said light beam, and means for also supporting said second named pair of ribbons on said base independently of said first named pair with said spaced parallel portions also in said light beam.

16. In sound recording apparatus, a light sensitive film, means for advancing said film uniform- 1y, means including a light source for optically projecting a substantially constant beam of light onto said film, means including a source of energy modulated in response to sound waves, a pair of ribbons having spaced parallel portions in said light beam vibrated in response to the frequency of said modulated energy for recording a frequency record of said sound'waves onto said film, another pair of ribbons'also having spaced parallel portions in said light beam vibrated in response to the amplitude of said modulated energy for recording an amplitude record of said sound waves onto said film jointly with said frequency record, and means including a base for tensionly supporting each pair of said ribbons on said base independently one of the other.

OSCAR A. ROSS. 

